Method for electrorefining metal and improved electrolytic metal plates produced thereby



Dec. 11, i956 A. WESLEY ET Al. 2,77398l5 METHOD FOR ELECTROREFINING METAL AND IMPROVED ELECTROLYTIC METAL. PLATES PRODUCED THEREBY Filed Aug. 2, 1952 2 ShBBtS-Sheel l Hm Ammin) HU) um HHHHUHH HHDUUHHHU JUNJUHUUH) Hummm mhmmml) Dec. 11, 1956 A. WESLEY ET AL 2,773,815

METHOD FOR ELECTROREFINING METAL AND IMPROVED ELECTROLYTIC METAL PLATES PRODUCED THEREBY Filed Aug. 2, 1952 2 sheets-sheet 2 WG- (AM United States Patent O METHOD FOR ELECTROREFINING METAL AND IMIPROVED ELECTROLYTIC METAL PLATES PRODUCED THEREBY Andrew Wesley, Plainiield, and Robert J. McKay, Basking Ridge, N. J., assignors to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware Applicatie August z, 1952, seal No. 302,304

7 claims. (ci. 204-12) The present invention relates to cathodes and cathode starting sheets for the electrolytic recovery of metal and, more particularly, to a method for producing cathode metal plates which are readily separable, dividable, or breakable along at least one line in a major face of the plates into pieces of predetermined smaller area, and to the product produced by said method.

Attempts have been made to provide readily dividable or separable cathode metal plates, e. g., electrolytic nickel cathode plates. Metal cathodes produced in electrolytic reiineries are customarily produced only in a standard size convenient to the refining process. When, as frequently happened, other smaller sizes of cathode sheet were required for industrial uses, the cathode sheets had to be sheared to the desired smaller size. Such shearing was an expensive operation requiring a powerful and expensive machine and much manual handling of the awkward cathode sheets. A customary method employed in electrolytic refineries to produce cathode metal is to grow thin cathode starting sheets of the metal to be recovered by plating upon an inert metal cathode, such as a stainless steel or an aluminum cathode, thereafter to strip the thin metal sheet, called starting sheet, from the inert cathode and to use this starting sheet as a cathode in the electroreiining operation to grow a cathode metal sheet approximately to 1/z inch thick. Metal is usually electrodeposited simultaneously upon both sides of the starting sheet in producing the final cathode metal sheet. The cathode sheets of tough, ductile metals such as nickel, copper, etc., obtained in this manner are usually very tough and diflcult to shear.

Prior attempts have been made to solve the problem solved by the present invention. Thus, U. S. Patent No. 2,392,614 to Prescott utilized slots cut in the starting sheet to create lines of weakness in the electrolytic metal, but this method suffers the disadvantage that the slots cannot be cut completely across the starting sheet and it is found that the portions of the final cathode metal sheet corresponding to the unslotted portions left to hold the starting sheets together are as tough and hard to divide as the remaining electrolytic metal away from the original locations of the slots and these tough portions make it diflicult to divide the metal yield rough, ragged edges when broken by bending.v

Although attempts were made to overcome the foregoing difculties and other diiculties, none, as far as we are aware, was entirely successful when carried into practice commercially on an industrial scale.

It has now been discovered that metal starting sheets used in electrorening operations can be treated such that the resulting electrolytic metal sheets can be readily parted or divided into pieces of smaller area to give clean edges at predetermined lines entirely across Vthe major 'faces ofthe sheet;'yet these electrolytic metal sheets are sucientl'y strong to vwithstand normal'shocks and stresses in handling.

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It is an object of the present invention to provide a method whereby metal cathodes are obtained in electrorefning which are dividable into metal sheets of predetermined smaller dimension. i

It is a further object of the invention to provide a method whereby dividable cathode metal sheets may be produced in electrorening without interfering with the normal operation of the electrorening process.

Another object of the invention is to provide a process for producing electrolytic nickelcathodes which are readily separable at predetermined lines extending across the electrolytic or cathode nickel sheet into sections of predetermined smaller area, said sections being characterized by substantially smooth, straight edges.

The invention also contemplates providing electrolytic metal cathode sheets which are readily dividable along predetermined lines on the major faces of the cathode into pieces of smaller area.

lt is a further object of the invention to provide electrolytic nickel cathode sheets which are readily dividable into pieces of the same thickness but of smaller area and which have smooth, straight edges. f

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing in which:

Figure 1 is a reproduction of a photograph taken at about three-fourths actual size and depicting the side view of a portion of a dividable nickel cathode produced in accordance with the present invention;

Figure 2 is a reproduction of a photograph taken at full size and depicting the fractured edge of a portion of a dividable nickel cathode after said cathode had been fractured along a predetermined line established by the process embodying the present invention.

Figure 3 is a view in elevation of a starting sheet prepared according to the invention;

Figure 4 is an enlarged partial cross-sectional view of the starting sheet of Figure 3, taken on the line 4 4 thereof;

Figure 5 is a View in elevation of an electrolytic metal plate produced according to the invention;

Figure 6 is au enlarged partial cross-sectional view of the plate of Figure 5, taken on the line 6 6 thereof;

Figure 7 is an elevational view of the plate of Figure 5 after it has been broken into sections by bending; and

Figure 8 is an enlarged partial cross-sectional view of two adjacent sections of the broken plate of Figure 7, taken on the line 8-8 thereof.

Generally speaking, the present invention contemplates dividable or separable electrolytic metal cathodes, e. g., nickel cathodes, and a method for producing the saine comprising forming thin metal starting sheets (e. g., sheets about 1,/2 inch in thickness but having substantial breadth and width to form the major faces thereof), preferably of the metal being produced electrolytically and of about the area of the desired nal electrolytic sheet; applying at least one line of a non-conducting resist across at least one face of said starting sheet, said line having a substantial width correlated to the thickness of the final cathode sheet; and thereafter depositing metal upon said face of said starting sheet to build up the cathode to a desired final thickness sucient to cover said lines of resist.

When metal is deposited upon both sides of the startingA vided by the invention comprise a metal starting sheet having at least one line of resist of critical width applied to at least one side thereof and a plate of electrolytic metal deposited upon said side to cover completely said about thrce-sixteenths inch thick.

The term iresist. as used herein means a material which can be applied to a metal surface in the form of an adherent, non-conducting coating resistant to the dissolving action of solutions used for cleaning and for electroplating upon such surfaces and includes non-conducting inks, lacquers, paints, varnishes, tapes, and/or films which may be applied in the form of lines having little thickness to the faces of the starting sheets.

lvWhen the lines of `resist having critical Width are applied to the faces of the starting sheets as contemplated in the present invention and metal is electrodeposited thereon, metal is not deposited initially upon the areas covered by the lines'of non-conducting resist. However,

in carrying out the present invention, metal is electrod'eposited upon the special starting sheet prepared in accordance with the invention until the electrolytic metal deposit completely covers over the line or lines of resist. In this manner, lines of division corresponding to the location of the` originally applied lines of resist are cre` ated inthe final electrolytic cathode metal plates along which the cathode metal plates may be parted or divided Vwith comparative ease to leave clean, straight edges; yet

the cathode metal plates are suiciently strong and rigid to withstand withoutbreaking the shocks and stresses encountered in shipping. By applying to the starting sheet a plurality ofY lines of resist which may be parallel, converging, intersecting, etc., in proper patterns such as rectangles, squares, etc., full-sized electrolytic metal plates are produced after 'electrodeposition' upon the thus-prepared starting sheet which may be divided into smaller shapes having required dimensions.

As noted hereinbefore, the lines of resist are applied to a relatively thin metal starting sheet which is usually itself made from electrolytic metal, and the electrolytic A metal deposit is built up thereon to form cathode metal plates. The thickness of the starting sheet is governed by practical considerations since the starting sheet must have suicient stiffness to maintain uniform distance from .adjacent electrodes in the Velectrorelining tanks without Y waving about or coming in contact with adjacent elec'- of.l resist by transverse bending rstin one direction to break the Vportion of electrolytic metal which is Vsubjected to tension by the bending action and then byY reversing the direction of the bend to break the electrolytic metal on the other side of the starting sheet. The 'starting sheet itself can then be broken by the application of very little additional pressure in bending. f course, the div-idable electrolytic metal plates can also bebroken along the lines of division 'provided in Vaccordance with the' present invention by a single bending operation, but the broken edges are likely to be rougher than when the preferred bending procedure aforementioned is employed. Other .methods of dividing the dividable electrolytic metal plates provided by the invention may also be employed, e. g., cutting, shearing, etc. Again, the invention may be 'ernployed to produce cathode plates having eleetioy'e meta-1 plated on only 'one side f the stair'ting sheet, in `ivlzich ca'se it iis unnecessary to apply resist to1 thesideof the starting she'ets 'which will not Abe plated.

4 The accompanying Figures l and 2 illustrate a dividable nickel cathode plate provided by the invention. Thus, Figure l shows a portion of a dividable nickel cathode plate produced in accordance with the present invention Y and Figure 2 shows the broken edge and one side of a portion of the dividable nickel cathode shown in Figure l after breaking at section II-II. The bulges or humps shown in Figures l and 2 and designated by the reference character 1 result from a design embossed in the starting sheet for the purpose of stilfening the starting sheet. ln Figure 2, the light-colored line 'running through the broken edge of the cathode is the thin nickel starting sheet which protrudes an average of only about 0.5 mm. from the fractured face. It will be noted from Figure 2 that the cathode nickel deposited upon the starting sheet has fractured to leave a smooth surface. The cathode metal shown in Figure 2 has also been broken along another line of division extending perpendicularly from the fractured face shown and the cathode metal depicted is held together along said perpendicular Vline of division by the starting sheet only. The dark areas in the fractured face adjacent the light-colored fracture of the starting sheet represent a relatively non-reecting portion char acterizing the line of division produced in the electrolytic nickel made in accordance With the present invention.

Figures 3 through 8 illustrate successive steps in the preparation and division of a dividable electrolytic metal plate according to the invention. Figure 3 is an elevational view of a starting sheet having a plurality of continuous lines of resist 2 applied 'across the faces thereof. Figure 4 is an enlarged sectional view` of a portion of the sheet of Figure 3, showing the lines 2 on both faces of the sheet in registered or superposed position. Figure 5 shows the finished dividable plate comprising the painted starting sheet on which metal has been electrodeposited to.

the desired thickness; and Figure 6 is a partial section of the finished plate of Figure 5, illustrating the manner in which the electrode'posited met-al bridges over and "substantially covers the lines of resist 2. Figures 7 and 8 illustrate, respectively, elevational and partial cross-sectional views of the plate after it has been broken into sections by bending. It will be noted that the deposited metal has broken smoothly and evenly along lines corresponding to the locations of the lines of resist on the starting sheet. Y

For the purpose .of giving those skilled in the art a better understanding of the invention and/or a better appreciation of the advantages of the invention, the following illustrative example is given:

A section of a starting sheet 0.031 inch thick was cleaned by degreasing and scrubbing with Wet pumice. Continuous lines of resist made of an air-drying lacquer commonly used in electroplating -as `a stop-cti lacquer about /s inch wide were applied at corresponding locations on each Iside of the starting sheet completely across eachrfacerof the starting sheet `to markY ott the' sheet in approximately '3-inch squares. The sheet was thereafter given a pretreatment torpromote adherence of electrodeposited nickel comprising anodic vexposure for 5 minutes at F. and 15 amperes per square foot in a bath containing vabout grams Aper liter vsulfuric acid, labout 50 grams per liter sodium chloride and about 5 grains per liter copper as copper sul-fate. vNickel was then electrodeposited upon both lsidesof the prepared starting sheet to produce a cathode havingy a total thickness of A 'load of 8000 .poundsr at .abend of ,6% broke one side of Y the deposit, and a floa ef 7G00 .pounds et Ja .bend ef 6 broke the other side of the deposit. A very straight smooth break was obtained as shown in the accompanying' Figuie 2. Another joint 3 inches long taken from said cathode was broken Yby bending, and it was found that the maximum load required to break the deposit on one side ofthe starting sheet was 1400 pounds at a bend of 14 while the deposit on the opposite side broke at a load of 1000 pounds vat a bend of 9.

In order to show the critical importance of the continuous line of resist having a critical width as contemplated by the present invention, another starting sheet was prepared and electroplated as in Example I with the exception that instead of using the continuous line of resist having critical width as required by the present invention, the starting sheet was marked oif on each side thereof with registering but discontinuous rows of thev same stop-off lacquer or resist as used in Example I but applied in the form of circular patches about l/s inch in diameter and spaced about 1%; inch apart. Nickel was deposited on both sides of the starting sheet to produce -a cathode plate having a total thickness of about 0.350 inch. This plate was broken in a tensile machine by bending a section 21/2 inches long along the line where the circular patches of resist had been placed. Three reverse bends of about 45 under a load of 8000 pounds were required to break the said section and a very rough and jagged fracture was obtained.

As indicated hereinbefore, the width of the resist line employed in making the dividable electrolytic plates provided by the invention is a critical feature of the invention. Thus, in one instance, when a nal nickel cathode thickness of about 1%; inch was produced, it was found that the cathode could not be broken by bending in a vise along a line of division resulting from the application upon registering sides of a starting sheet having original resist lines ly@ inch wide, although the same cathode broke readily when bent in the same manner along a line of division resulting from resist lines /s inch wide. When resist lines Wider than the width indicated herein are employed, a strong, heavy bead of electrolytic metal builds up along the edges of the resist line to produce too great `a local increase in thickness of deposit at these locations with the result that difficulties may be encountered in the clectrorening cell and that increased force is again necessary to bend or break the nished plate and it is found that there remains along the fractured edge a sharp edge of the original starting sheet protruding beyond the fractured electrodeposit. The following formula aiords a convenient means of determining the proper critic-al width of resist line to employ in carrying out the present invention:

2T T W-i-lwhere W=width of each resist line in inches,

T=thickness in inches of electrodeposited metal on the face upon which the line (or lines) of resist is applied.

Thus, where metal is electrodeposited on both faces of a starting sheet to yield a cathode having a total thickness of 3% inch, i. e., an electrodeposit on each face of about s inch, the width of each line of resist on each face will be approximately 1A; inch. If a resist line is used having a width either greater than or narrower than that determined by the above-mentioned formula, the deleterious effects discussed hereinbefore will then result.

Numerous types of resists may be employed in carrying out the present invention, including vinyl resin base paints (such as sold under the mark R-ack Coating No. 266), synthetic polymer preparations requiring a baking treatment (such as sold under the mark Unichrome Coating 218X), air-drying synthetic resin stop-offs (such as sold under the trade mark Microstop), chlorinated hydrocarbon waxes applied by melting (such as sold under the trade mark Halowax), and insulating impregnated tapes (such as sold under the trade mark Microtape). It will be recognized by those skilled. in the art that resists such as the foregoing can be applied to metal sheets by conventional means such as brushing, spraying, etc. Certain types of resists can be obtained in tape form and applied per se to the metal starting sheets. lt should be borne `in mind that certain resist compositions which produce coatings satisfactory for the purpose of creating lines of weakness in cathode metal plates may contain solvents or soluble ingredients which will disturb the characteristics of the plating bath and cause pitting, etc. Accordingly, the particular resist selected should be tested for its eiect upon plating bath performance.

An outstanding feature of the present invention resides in the fact that starting sheets can be treated in such manner that the lines of division created in the nal cathode sheet can extend to the edge of the starting sheet, i. e., the resist line or the network of resist lines employed can extend completely -across the starting sheet. In this manner, difficulties in parting, breaking or dividing the final cathode plate are minimized since no section of the line of weakness produced in the final electrolytic metal plates in accordance with the invention has the strength and toughness of the remaining portions of the cathode metal plate. This is particularly important at the edges of the as-plated cathode plate, since normally there is a tendency for the current density to increase at the edges with the result that the plate at the edge frequently has a thick, heavy bead and is proportionally harder to bend or break than the plate at the interior portions of the cathode sheet.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art 'will readily understand.- Thus, while the invention has been described principally 'in connection with the electrorening of nickel, those skilled in the art will appreciate that the invention is also applicable in the electrorefining of other tough, ductile metals such as copper, etc. Such modifications and variations are considered to be Within' the-purview and scope of the invention and appended claims.

We claim:

l. As a new article of manufacture, a composite dividable electrolytic nickel plate comprising an imperforate nickel starting sheet having a plurality of continuous lines of resist applied at corresponding locations on opposite faces thereof and extending across said faces, and an electrolytic nickel deposit upon said faces covering said lines of resist and having a thickness of nickel deposit upon each face that is related to the width of a line of resist on the face as determined by the following formula:

W s i1 0 wherein W is the width of the line of resist and T is the thickness of the nickel electrodeposit on the face to which said line of resist has been applied, said plate being readily dividable into pieces of smaller area having substantially smooth and straight edges by bending along lines corresponding to the locations of said lines of resist.

2. As a new article of manufacture, a composite dividable electrolytic metal plate comprising an imperforate starting sheet having at least one continuous n-arrow line of resist applied across a face thereof, and an electrolytic metal deposit upon said face covering said line of resist and having a thickness that is related to the width of the line of resist on the face as determined by the following formula:

W- s i1 0 wherein W is the width of the line of resist and T is the thickness of the metal electrodeposit on the face on which nickel plate which comprises applying across the faces of a 'nickel starting sheet a plurality of continuous lines of resist about Vs inch wide and in registering locations on each face of said sheet, and electrodepositing nickel upon both sides of said starting sheet to cover said lines vof resist and to produce 'an .electrolytic nickel plate about inch thick and having a plurality of lines along which said plate is readily dividable into pieces of smaller area by bending along :Ii-nes corresponding in location to lthe lines jof resist applied to the starting sheet,

4. A process for producing a dividable -electrolytic nickel plate which comprises applying across the faces of a nickel starting sheet at least one continuous narrow line of resist at corresponding locations on opposite faces of said sheet, and el'ectrodepositing nickel upon both sides of said starting sheet until said lines of resist are covered with nickel and `until -a thickness of electrodeposited nickel is obtained which is related to the Width of a line of resist on the face as determined by Vthe following formula:

wherein W is the width of line of resist and T is the thickness of metal electrodeposited on the face onto which said line of resist has been applied, to thereby produce an electrolytic nickel plate having at least one line along which said plate is readily dividable by bending corresponding `in location to the line of resist applied to the starting sheet.

5. A process for producing a composite dividable electrolytic metal plate which comprises applying across a face of an imperforate metal starting sheet at least one continuous narrow line'of resist, and electrodepositing metal u pon vsaid -face until said line of resist is covered 'with metal :and until a thickness of electrodeposited metal is obtained which is related to the width of the line of resist on the `face as determined by the following formula:

:aria

wherein W is the width of line of resist and T is the thickness of metal electrodeposited on the face on which said line of resist has been applied, to thereby produce an electrolytic `metal plate having at least one line along which said plate is readily dividable '.by bending corresponding in location tothe line of resist applied ito the starting sheet. y I

6. The process for producing a dividable electi'dlyti'c metal plate, which comprises applying across the' opposite major faces of a metal starting sheet at 'least one continuous line of resist at corresponding locations on said faces and electrodepositing on said faces a thickness of metal deposit that isrelated tothe width' of aline of resist on the vfaces as determined by the following formula:

:nia

wherein W is thewidth of the line rof resist and T is'fthe thickness of the metal electrodeposited on the faces 'to which said line of resist has been applied, therebyjproducing an electrolytic metal plate which is readily dividable f by bending along at least one line corresponding in'location to the line of -resist applied to a metal starting sheet. 7. As -a new article of manufacture, a dividable nickel cathode comprising a nickel starting sheet having atleast one continuous line of resist extending across each vface of said starting sheet and in registering location thereon, anda nickel electrodeposit upon both faces of said starting sheet and embedding said lnies of resist, said electrodeposit of nickel upon each face of said starting sheet being of a thickness that is related to the Width of the line of resist on the face as determined by the following formula:

References LCited in the file of this patent UNITED STATES PATENTS 426,788 Farmer Apr. 29, 1890 684,291 McCoy Oct. 8, 1901 2,392,614 Prescott Jan. 8, 1946 FOREIGN PATENTS 474,790 Germany Apr. 13, 1929 

1. AS A NEW ARTICLE OF MANUFACTURE, A COMPOSITE DIVIDABLE ELECTROLYTIC NICKEL PLATE COMPRISING AN IMPERFORATE NICKEL STARTING SHEET HAVING A PLURALITY OF CONTINUOUS LINES OF RESIST APPLIED AT CORRESPONDING LOCATIONS ON OPPOSITE FACES THEREOF AND EXTENDING ACROSS SAID FACES, AND AN ELECTROLYTIC NICKEL DEPOSIT UPON SAID FACES COVERING SAID 